1. Field of the Invention
The present invention relates to a gas compression apparatus for reciprocating compressor, and more particularly, to a gas compression apparatus for reciprocating compressor that is capable of controlling a piston stroke distance to control a compression amount of a compressed refrigerant gas and capable of minimizing a dead volume.
2. Description of the Background Art
In general, a compressor compresses a fluid. A reciprocating compressor of the present invention is operated that a piston directly connected to a motor which generates a linear reciprocal driving force is linearly and reciprocally moved within a cylinder, so as to compress a refrigerant gas.
As shown in FIG. 1, the reciprocating compressor includes a closed container 10, a reciprocating motor 20 installed in the closed container 10 and generating a linear reciprocal driving force, a rear frame 30 and a middle frame 40 respectively supporting both sides of the motor 20, a front frame 50 coupled to one side of the middle frame 40, a cylinder 60 for being coupled to the front frame 50 to have a predetermined distance along an axial direction with the reciprocating motor 20; a piston 70 connected to the reciprocating motor 20 and inserted into the cylinder 60, making a linear reciprocal movement in the cylinder 60 upon receiving the linear reciprocal driving force of the reciprocating motor 20; a valve assembly 80 combined to the cylinder 60 and the piston 70 and sucking and discharging gas into the cylinder according to a pressure difference generated by the reciprocation movement of the piston 70; and a resonance spring unit 90 elastically supporting the linear reciprocal movement of the reciprocating motor 20 and the piston 70.
The reciprocating motor 20 includes a cylindrical outer stator 21 fixedly coupled to the rear frame 30 and the middle frame 40; an inner stator 22 inserted into the outer stator 21 with a certain distance; a winding coil 23 wound inside the outer stator 21; and an armature (A) inserted to be linearly and reciprocally movable between the outer stator 21 and the inner stator 22 with a certain distance, respectively.
The armature (A) includes a cylindrical magnet holder 24, and a plurality of permanent magnets 25 coupled to the outer circumferential face of the magnet holder 24 along the circumferential direction at regular intervals. The armature (A) is coupled to the piston 70.
The resonance spring unit 90 includes a support 91 formed bent to have a predetermined area, one side thereof being coupled to one face of the piston 70 or the armature (A) so that the support can be positioned between the front frame 50 and the middle frame 40, a front spring 92 positioned between the front frame 50 and the support 91, and a rear spring 93 positioned between the support 91 and the middle frame 40.
The valve assembly 80 includes a discharge cover 81 covering the compression space (P) of the cylinder 60, a discharge valve 82 being positioned inside the discharge cover 81 and opening and closing the compression space (P) of the cylinder 60, a valve spring 83 elastically supporting the discharge valve 82, and a suction valve 84 coupled at an end portion of the piston 70 and opening and closing a refrigerant suction passage (F) formed in the piston 70.
A discharge pipe 2 is coupled at one side of the discharge cover 81 to guide gas compressed to a high temperature and high pressure to be discharged, and a suction pipe 1 for guiding the refrigerant gas to be introduced into the closed container 10 is coupled at one side of the closed container 10 so as to be positioned at the side of the rear frame 30.
The operation of the conventional reciprocating compressor constructed as described above will now be explained.
First, when current flows through the winding coil 23 as a power is supplied to the reciprocating motor 20, the armature (A) having the permanent magnet 25 is linearly and reciprocally moved owing to the interaction between the magnetic flux formed at the outer stator 21 and the inner stator 22 by the current flowing through the winding coil 23 and the permanent magnet 25.
As the linear reciprocal driving force of the armature (A) is transferred to the piston 70, the piston 70 is linearly and reciprocally moved in the compression space (P) inside the cylinder, and at the same time, the valve assembly 80 is operated so that gas is sucked into the compression space (P) of the cylinder, compressed and discharged. And this process is repeatedly performed.
The spring unit 90 stores and discharges the linear reciprocal kinetic movement force of the reciprocating motor 20 as an elastic energy and causes a resonance movement.
As shown in FIG. 2, the reciprocating compressor is assembled with its initial position (a) set in such a manner that the end portion of the piston 70 positioned inside the cylinder 60 is positioned at the center of a maximum upper dead point (Hmax) and a maximum lower dead point (Lmax), of which the distance between the two points is a maximum stroke distance (Smax).
In general, as a voltage of a power is controlled, an arbitrary stroke distance (S1) between an arbitrary upper dead point (H1) and an arbitrary lower dead point (L1) is moved with reference to the initial position (a), the right center of the maximum upper dead point (Hmax) and the maximum lower dead point (Lmax), so as to compress the refrigerant gas.
That is, in case where a relatively much amount of refrigerant gas is to be compressed and discharged in the compression space (P) of the cylinder 60, as shown in FIG. 3, the stroke distance (S2) of the piston 70 is increased, though shorter than the maximum stroke distance (Smax), to increase the amount of the compressed refrigerant gas.
Meanwhile, if a relatively small amount of refrigerant gas is to be compressed and discharged in the compression space (P) of the cylinder 60, as shown in FIG. 4, the stroke distance (S3) of the piston 70 is made to be smaller.
At this time, the piston is moved on the basis of the initial position (a), the right center of the maximum upper dead point (Hmax) and the maximum lower dead point (Lmax). Thus, if the stroke distance of the piston 70 is made to be larger, the distance between the upper dead point 70 of the piston and the bottom surface of the discharge valve 82, that is, a top-clearance, is shortened. Meanwhile, if the stroke distance of the piston 70 is made to be smaller, the top-clearance, that is, the distance between the upper dead point 70 of the piston and the discharge valve 82, is lengthened.
However, though the conventional structure has an advantage in that the compression amount of the refrigerant gas can be controlled by controlling the stroke distance of the piston under the voltage control, so that the gas can be compressed as much as desired, since the piston is always moved along the stroke distance set on the basis of the initial position, the middle between the maximum upper dead point and the maximum lower dead point, the top-clearance is increased. Due to the increased top-clearance, a dead volume is increased, degrading a compression efficiency.
Therefore, an object of the present invention is to provide a gas compression apparatus for reciprocating compressor that is capable of controlling a piston stroke distance for a compression amount control of a refrigerant gas and capable of minimizing a dead volume.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a gas compression apparatus for reciprocating compressor including: a reciprocating motor generating a linear reciprocal driving force; a compressing cylinder positioned with a predetermined distance from the reciprocating motor; a position controlling cylinder positioned with a predetermined distance from the compressing cylinder; an initial position variable type piston inserted into the compressive cylinder and the position controlling cylinder, coupled to the reciprocating motor, receiving a driving force of the reciprocating motor and being linearly and reciprocally moved within the compressing cylinder and the position controlling cylinder; a resonance spring including a resonance movement of the initial position variable type piston; a discharge cover coupled to cover an end portion of the compressing cylinder and forming a discharge chamber for discharging a compressed gas; a valve unit for sucking gas into the compressing cylinder through a gas suction passage formed inside the initial position variable type piston according to the linear reciprocating movement of the initial position variable type piston and discharging the gas compressed in the compressing cylinder into the discharge chamber of the discharge cover; a connection pipe for guiding a portion of the gas pressure discharged into the discharge chamber of the discharge cover to be introduced into the position controlling cylinder; and a pressure controlling unit being mounted at one side of the connection pipe and controlling a pressure inside the position controlling cylinder with the pressure of the gas discharged from the discharge chamber.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.